A Crh-defined insular cortex-brainstem-thalamic circuit regulates anxiety-related behavioral states

Anxiety disorders are among the most prevalent and debilitating psychiatric conditions, yet the neural circuits underlying anxiety-related states remain incompletely understood. Here we identify a cortical-brainstem-thalamic pathway in which Crh-expressing neurons in the anterior and middle insular cortex (a/mIC) engage the parabrachial nucleus (PBN), which in turn recruits the posterior paraventricular thalamic nucleus (pPVT) to contribute to anxiety-related behavior. Single-cell calcium imaging reveals that the predator odorant 2-methyl-2-thiazoline (2-MT) and footshock recruit partially overlapping populations of PBN-projecting a/mIC neurons; neurons activated by both stimuli exhibit increased activity during open-arm approach in the elevated plus maze. Exposure to 2-MT increases corticotropin-releasing factor (CRF) signals in the PBN, where CRF enhances PBN neuronal excitability and CRF receptor 1 (CRFR1) signaling facilitates a/mIC-terminal-evoked firing. Inhibition of Crh⁺ a/mIC-PBN projections, Crh knockdown in the a/mIC, or blockade of CRFR1 signaling within the PBN attenuates 2-MT-induced anxiety-like behavior. Human neuroimaging further reveals stronger functional coupling within a putative homologous aIC-PBN-pPVT network in individuals with anxiety symptoms, and the strength of this coupling correlates with anxiety severity. Together, these findings define a molecularly specified insular circuit that contributes to anxiety-related behavioral states.